This invention relates to novel antitumor agents and intermediates useful for their preparation. More particularly, the present invention relates to 7-deoxytaxol, 7-deoxy-10-desacetyloxytaxol and derivatives thereof.
Taxol was first isolated from the stem bark of Western Yew, Taxus brevifolia Nutt (Taxaceae) and has the following structure (with the (C)2'-, 7-, 10- and 13th-positions indicated): ##STR2## In clinical trials sponsored by the National Cancer Institute (NCI), taxol has shown promising results in fighting advanced cases of ovarian, breast, and other cancers. Taxol has recently been approved for the treatment of metastatic carcinoma of the ovary.
Taxol is unique among antimitotic drugs in that it promotes the assembly of stable microtubules from tubulin even under otherwise unfavorable conditions. The drug binds to microtubules, stabilizing them from depolymerization, thus disrupting the tubulin-microtubule equilibrium and consequently inhibiting mitosis. The mechanism of action, toxicology, clinical efficacy, etc. of taxol are reviewed in a number of articles, such as in the article by Rowinsky et al. in Taxol: A Novel Investigational Antimicrotubule Agent, J. Natl. Cancer Inst., 82: pp 1247-1259 (1990).
Since the discovery of its significant effectiveness in cancer treatment, many laboratories have launched programs to design taxol analogues in search of better pharmacological profiles. Out of such a program, for example, was the discovery of taxotere of the formula ##STR3## See, Biologically Active Taxol Analogues with Deleted A-Ring Side Chain Substitutents and Variable C-2' Configurations, J. Med. Chem., 34, pp 1176-1184 (1991); Relationships between the Structure of Taxol Analogues and Their Antimitotic Activity, J. Med. Chem., 34, pp 992-998 (1991).
Relatively little is known about structure-activity relationships at either the (C)7th- or (C)10th-position of taxol. For example, Kingston et al. discuss the structural activity relationships of certain (C)7-esters and an epi-derivative only on a limited basis in the Journal of Natural Products: The Chemistry of Taxol, a Clinically Useful Anticancer Agent, 53, No. 1, pp 1-12 (1990). As a part of our goal to investigate the structural requirements for activity essential in the taxol area, we have been able to completely remove the (C)7- or (C)7-/(C)10-substituents in taxol and discovered that these deoxygenated taxol derivatives still retain antitumor activity. Thus, it is the intention of this invention to provide 7-deoxytaxol, 7-deoxy-10-desacetyloxytaxol and derivatives thereof.